hterm: terminal: use local color state for text overlays
hterm: terminal: use local color state for text overlays

If the fg/bg colors are changed on the fly, we probably want the
overlays to respect those settings as they'll more likely stand
out relative to the current display than whatever the user has
previously saved.

Change-Id: I0125da60ea29e76a138e9966e9e3a6b7ac0cf55c
Reviewed-on: https://chromium-review.googlesource.com/c/apps/libapps/+/2199356
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Joel Hockey <9ecfc52dc2ffef73afac73f3495f294aeddf1231@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm